(MONEY Magazine) – Jackie Cutlip, managing director of reservations for American Airlines, oversees the training of 4,000 agents.

Q. Don't frequent fliers always get the best seats? A. We do put a hold on certain seats for our most frequent travelers, typically aisle seats and seats close to the front of the plane. But if those seats aren't booked four hours before departure, they're released to agents at the airport, so you have another chance to get them when you check in. We also hold seats for people with disabilities until 24 hours before a flight, and we release seats 15 minutes before departure for anyone who hasn't shown up. All those seats are under airport control, so check with a ticket agent or the self-serve kiosk as soon as you get to the airport. You can also ask at the gate 15 minutes before departure.

Q. Is there a best time to book? A. Early, when more seats are available. You can book a seat almost a year in advance, and you should always reserve your seat at the time you book.

Q Does reserving seats on an airline's website help? A The seat maps online are real-time--you see the same thing that a reservation agent sees. So yes, it helps you see how full a flight is and which seats are still available.